Synthesis And Property Analysis Of Phosphate Phosphors Used For WLED

White light-emitting diodes have been paid increasing attention due to the advantages such as high brightness,small size,long lifetime,energy saving and environmental friendliness.However,most of the white LED phosphors at present are suffering from problems like low luminous efficiency,poor color rendering index,high color temperature,high cost and so on.Nowadays,the major W-LED in the market are phosphor-converted.However,there are relatively few phosphors that have hitherto been suitable for the excitation of ultraviolet or blue LED semiconductor chips with higher luminous efficiency and thermal stability.Therefore,the exploration and research of a new system of white light LED fluorescence has become the leading issue of luminescent materials research.In this dissertation,Eu³⁺,Tb³⁺,Sm³⁺and other luminescent ions have been chosen as activator,and several new phosphate matrix systems have been taken as the research object.Through the optimization exploration of the host system and the doping of luminescent ions,different color luminescence can be obtained.The energy transfer between different luminescent centers enables the luminescent color to be adjustable,and then the highly efficient phosphate-based fluorescence excited by ultraviolet light is designed and prepared.In this paper,the white phosphorus calcium and strontium-cerium apatite structure type phosphate-based fluorescent materials were synthesized by solid state reactions.And their crystal structures,photoluminescence spectra,fluorescence kinetics,energy transfer of luminescent ions,and colorimetry were analyzed in detail.The results obtained include the following three aspects:1?A family of whitlockite-type orthophosphate phosphors with nominal formula CMKP:0.01Eu²⁺,nMn²⁺?n=0–0.8?were synthesized via the high-temperature solid-state reaction method.The phosphors exhibit simultaneously blue emission of the Eu²⁺ion and red emission of the Mn²⁺ion upon the excitation of UV light through the partial energy transfer.The energy transfer from the Eu²⁺to the Mn²⁺ions has been proved to be a resonant type via a dipole–quadrupole mechanism based on the Dexter's theoretical model,and the energy transfer efficiency increases with an increase in Mn²⁺concentration.The emission colors of the obtained phosphors can be varied from blue through white and eventually to purplish red by properly tuning the doping content of Mn²⁺with a fixed Eu²⁺concentration in CMKP:0.01Eu²⁺,nMn²⁺phosphors.Especially,white light emission from the CMKP:0.01Eu²⁺,0.4Mn²⁺phosphor with CIE coordinates of?0.338,0.253?and a CCT of 4752 K was realized.These results indicate that the developed phosphor has significant potential to be a single-phased white-emitting conversion phosphor for ultraviolet-chip-based white LEDs.2?A group of Tb³⁺,Eu³⁺co-doped Sr₃LaNa?PO₄?₃F phosphors were prepared via conventional high temperature solid state method.Under 369 nm excitation,owing to efficient energy transfer of Tb³⁺?Eu³⁺,the emission spectra both have green emission of Tb³⁺and red emission of Eu³⁺.The energy transfer of Tb³⁺and Eu³⁺was confirmed by the variations of excitation and emission spectra and Tb³⁺/Eu³⁺decay lifetimes in Sr₃LaNa?PO₄?₃F:Tb³⁺,Eu³⁺.The most possible mechanism of energy transfer is dipole-dipole interaction by Dexter's theoretical model.The maximum value for energy transfer efficiency is 43.71%,this indicates that Tb³⁺transfer partly energy to Eu³⁺,so we can change the concentrations ratio of Tb³⁺/Eu³⁺to generate color tunable phosphors.The color tone can tuned from yellowish-green through yellow and eventually to reddish-orange with fixed Tb³⁺content by changing Eu³⁺concentrations.The results show that under UV excitation,combining the blue emitting BAM:Eu²⁺(BaMgAl₁₀O₁₇:Eu²⁺)phosphor with our developed SLN:0.20Tb³⁺,nEu³⁺?n=0-0.20?phosphors can fabricate white LED systems with high chromaticity quality.3?A series of Sm³⁺doped Sr₃LaNa?PO₄?₃F phosphors were prepared by high temperature solid state reaction.Under the excitation of 403nm,the luminescence intensity of Sr₃LaNa?PO₄?₃F:0.05Sm³⁺phosphor is the largest.In order to improve the luminescence intensity of Sr₃LaNa?PO₄?₃F:0.05Sm³⁺phosphors,alkali metal ions Li⁺,Na⁺,K⁺were added as charge compensators.The results show that Li⁺,Na⁺and K⁺can obviously improve the luminescence intensity of the phosphor,and the enhancement effect of Li⁺is the most obvious.